This invention relates generally to a brake system for a construction vehicle, and more particularly, to a parking brake switch for an electro-hydraulic brake system.
In a conventional electro-hydraulic brake system for a vehicle, such as a construction vehicle, the parking brake associated with such vehicle is typically automatically operated and engaged when stored energy for the service brake system is depleted. In contrast, the parking brake can not be deactivated or disengaged until the energy storage device for the service brake system is charged to an extent as to provide for satisfactory service brake application. During an electrical power failure, it is also possible that the brake system may fail and the parking brake may not be maintained in its operator selected (released) state. There are also situations that may occur, such as a single electrical failure, in which the parking brake may be automatically applied while the vehicle is moving. These are all disadvantages associated with a conventional electro-hydraulic brake system.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a parking brake switch for a vehicle includes at least three separate contacts and a contacting surface, the switch being positioned between an actuated state and a deactuated state, a first contact being connected to a brake valve associated with an electro-hydraulic braking system, a second contact being connected to a pair of electronic control modules, and a third contact being connected to the pair of electronic control modules and to a coil, the contacting surface of the present switch being adapted to engage all of the first, second, and third contacts when the switch is in the actuated state.
In another aspect of the present invention, a parking brake switch for a vehicle for controlling operation of a parking brake associated with an electro-hydraulic braking system includes an operating portion and a contacting surface, the switch being biased between an activated state and a deactivated state, a first contact connected to a brake valve associated with the electro-hydraulic braking system, a second contact connected to a first electronic control module and a second electronic control module, and a third contact connected to the first and second electronic control modules, the contacting surface of the present switch being adapted to engage all of the contacts when the switch is in the actuated state.